Significantly enhancing current carrying performance of MgB₂ superconductor with natural dopants carbon nanoparticles and rare earth elements derived from <i>Dicranopteris pedata</i> waste

Abstract Carbon doping has always played an irreplaceable and important role in improving the performance of MgB 2 superconductors. However, the excessive suppression of T c by carbon elements and its excessive accumulation at grain boundaries make it difficult to realize its potential to enhance the performance of MgB 2 in the preparation of practical materials. In addition, introducing magnetic flux pinning centers that are more effective than interface pinning is another challenge faced by MgB 2 . In this study, a mixture of carbon nanoparticles and trace rare-earth elements (CNPs/REEs) obtained from high-temperature calcination of Dicranopteris pedata waste was used as a dopant, which can effectively introduce an appropriate amount of carbon into the MgB 2 lattice in short-term low-temperature reactions to enhance the irreversibility field ( H irr ) of MgB 2 . Moreover, the residual CNPs and rare-earth impurities that have not entered the lattice can be highly dispersed in MgB 2 , serving as point pinning centers, and at the same time, limiting the growth of MgB 2 particles, which further strengthens the role of the grain boundary pinning force. The synergistic consequence of these doping effects leads to a significant increase in J c throughout the entire magnetic field range (0–10 T) at 4.2 and 20 K. As a result, J c @3 T at 4.2, 10, and 20 K increased from 90, 41, and 10 kA cm −2 for the undoped MgB 2 to 230, 87, and 20 kA cm −2 for the C-005 sample, respectively. At 20 K, the H irr value reached more than 5 T (doping amount x = 0.05). It was also found that the irreversibility field is governed by the giant flux creep characteristic as the dopant concentration increases, and the main pinning mechanism of the doped samples is still the grain boundary pinning.